One of the biggest manhunts South Africa has ever seen was under way this weekend as police searched for Ananias Mathe - 'the devil's child'.

South Africa's most dangerous criminal and the country's most slippery prisoner made a dramatic prison breakout last week, apparently by smearing his body with petroleum jelly and squeezing through a tiny window.

But doubts have now been thrown on the official account of the daring escape by Mathe, 27, who faces 51 charges for crimes including murder, rape, armed robbery and hijacking, from the highest-security wing of Pretoria's C-Max prison, a jail from which no one had ever escaped in its 36-year history.

Sources close to the case believe he must have had inside help. Mathe had already fled police custody in 2005 and it took police nine months to track him down, so they put him in a special cell under high surveillance. Yet last week Mathe managed to free himself from handcuffs, strip and cover himself with Vaseline, pry out a bulletproof window and slither through the 8in by 23in hole.

He lowered himself down the wall, stopping to add insult to injury to warders by scrawling, 'Fuck you' on the wall. In their desperate scramble to catch Mathe again, police have made two arrests - one man was found not to be Mathe, but charged for possession of dagga (marijuana) anyway. Another unfortunate lookalike was shot in the leg when he tried to run away from a police ambush. It was not Mathe but the Rev Motlotlo Rabotapi.

'He must be the devil's child himself because we get new leads every day but he has not yet been arrested,' investigating officer Arnold Boonstra told The Observer. 'He seems to have the luck of the devil. I will not sleep until we catch him.'

This would all be a farcical comedy of errors if Mathe did not have such a fearsome reputation as a ruthless criminal responsible for a string of brutal crimes. The young Mozambican ran a gang of 40 who carried out brazen armed robberies and car hijackings. 'Rape is one of his trademarks. If a woman was one of his robbery victims, then he raped her,' said Johan Burger, a crime and security analyst at Pretoria's Institute for Security Studies.

Mathe specialised in robbing company vans transporting cash to banks. Gangs of 15 to 20 heavily armed men attack in broad daylight. So far this year there have been 468 such 'cash in transit' robberies and more than £6.6m has been stolen.

Newspapers have dubbed Mathe 'the Houdini of C-Max'. But virtually everyone who is close to the case believes that he received assistance from corrupt prison officials. 'Even Houdini himself could not have escaped from C-Max,' said Burger. 'There's no way he got out unaided. Only corruption could have got him out of that prison.'